1. Field of the Invention
The present invention generally relates to an oxide semiconductor thin film transistor (TFT) and a method for manufacturing the oxide semiconductor TFT.
2. Description of Related Art
A liquid crystal display is mainly constituted by a thin film transistor (TFT) substrate, a color filter substrate and a liquid crystal molecule layer disposed between the two substrates. There are multiple TFTs disposed on the TFT substrate, and each of the TFTs mainly includes a gate electrode, a gate dielectric layer, a semiconductor layer, a source electrode and a drain electrode. The semiconductor layer may be made of a material including amorphous silicon, polycrystalline silicon, microcrystalline silicon, monocrystalline silicon, organic semiconductors, oxide semiconductors or other suitable materials.
However, compared with the amorphous silicon TFT, the oxide semiconductor TFT possesses higher carrier mobility and thus exhibits better electrical performance. The oxide semiconductor usually needs to be annealed to stabilize the electrical performance of the oxide semiconductor TFT. In general, the temperature of the annealing process should be higher than or equal to 350° C.
Nevertheless, when a metal is exposed in a high temperature furnace during the annealing process, the metal would be oxidized so as to increase the impedance which severely affects the signal transmission. In view of this, there is a need for an improved method for manufacturing an oxide semiconductor TFT to solve the above problems.